Stand base



FIG. 1 is a perspective view of a stand base;

FIG. 2 is a top view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a right side view thereof.

Shading forms no part of the claim. Broken lines form no part of the present claim. 

CLAIM The ornamental design for a stand base, as shown and described. 